What is ISO? | Photography Definition, Tips, and Examples

What is ISO?

ISO is the camera setting that can either brighten or darken your shot. The higher your ISO is, the brighter it will become.

Its function aides’ photographers that have already found the perfect aperture and shutter speed but are faced with an underexposed shot. ISO also gives the photographer the flexibility to change the settings without worrying about brightness.

This brightness does come at a price though. Photographers who use too much ISO will face graining or commonly known as noise, making the photo less appealing.

The trade-off reminds photographers to only use ISO when they are in a pinch. Photographers will try to achieve brighter photos by using an aperture or shutter speed. Only using their ISO as their last resort.

Although it may sound like ISO is just like brightening an image on your PC it is still different. It quickly became a misconception since it does sound similar.

However, ISO provides an unrivalled quality when making your image brighter. I highly recommend using a high ISO rather than making the image brighter using Lightroom.

What Does ISO Stand For?

Interestingly, the ISO meaning does not have much correlation with its acronym.

The acronym itself stands for “International Organization for Standardization”. Why isn’t it “IOFS” then? I do not know, maybe ISO just sounds better back then.

The organization works with standard institutes from 150+ countries to develop technology and product standards. The standard makes the development of future products more efficient, safer, and cleaner.

ISO leads to products that are standardized for consumers.

There two film standards known as ASA and DIN were then combined into ISO around 1974. Now the two standards are referred to as ISO.

Initially, ISO was only referred for film sensitivity. As time passed by, it was then adopted by digital camera manufacturers. The purpose was to maintain the brightness levels present in films.

What are Common ISO Values?

ISO starts at the base level of 100. Each camera model has its own range of ISO values or ISO speeds. The usual set will look like this:

  • ISO 100
  • ISO 200
  • ISO 400
  • ISO 800
  • ISO 1600
  • ISO 3200
  • ISO 6400 (High ISO)

The number can still go over 6400. The highest ISO that I know of is 4.560.000 which is available on Canon’s craziest “hypersensitive” ME20F-SH camera.

Each ISO will approximately double the light of the previous ISO. The brightness of an ISO 200 is the brightness of an ISO 100 doubled.

While we are on the ISO value, let us briefly talk about base ISO.

Your camera’s lowest native ISO is called the base ISO. The base ISO will give you the best image quality, as it minimizes the occurring noise.

Your usual digital DSLR camera will have an ISO 100 as its base. While some of the older models will have a base ISO of 200.

iso light
Photo by Asad Photo Maldives

How Does ISO Affect a Photo?

ISO photography is highly situational. ISO helps you brighten photos, but if you use an ISO that is too high then there will be too much noise.

ISO itself affects the noise levels and dynamic range. Lower ISO provides a minimal amount of noise with a high dynamic range. The dynamic range will give the much-needed flexibility in post-processing.

Luckily, full-frame DSLR cameras have a better time handling noise. Since they have larger sensor compared to compact cameras.

So, what is the relation between ISO and Megapixel?
Well, let us think of the megapixel as a school while the ISO becomes the student. In order to fit more students into school without overcrowding it, you should increase the school’s size, right?

A larger school can handle more students. Which translates to more megapixels to make an image more resistant towards higher ISO.

While the compact camera will start displaying noise at ISO 800. The full-frame DSLR camera can have a minimal amount of noise at ISO 3200. That is how ISO affects the noise depending on a camera’s sensor.

Using ISO is not as easy as “If bright day then use small ISO if dark use high ISO.”

Well, to a certain extent it can work like that. But on future occasions, you might need to know more.

Since both aperture and shutter speed will affect incoming exposure. I highly recommend you read the article on the respective topics first.

But in a simple way they both affect the exposure on your images:

iso night
Photo by eberhard grossgasteiger


Larger apertures (f/1.4, f/2, f/2.8) lets in more light than its counterparts, making photos brighter. However, large apertures will mainly focus on the foreground and blur the background.

Smaller apertures (f/11, f/16, f/22) let in a tiny amount of light, eventually making the photos dark. But, smaller apertures provide the photo with a thorough sharpness from front to back.

Shutter Speed

Faster shutter speeds (1/4000, 1/2000) allows you to “freeze” fast-moving objects. But, it only lets in a minimal amount of light because of its speed.

Longer shutter speeds (1 second or more) will allow more light to hit the camera’s sensor. This makes the images considerably brighter, the longer the brighter. But, motion blur is bound to happen.

These two settings will already tamper with each other’s total exposure. This is where you should introduce your ISO to the mix since your aperture and shutter speed can only do so much.

ISO will increase the overall brightness of your photos. This makes it highly favored by photographers who shoot in low-light condition, photograph fast objects at close range, or photographers that want to avoid underexposing their shots.

What happens if ISO is Too Low?

So now you have ISO explained. But do you know how and when to apply that knowledge?

To start out with your photography journey, it is highly recommended to use the base ISO. Depending on your camera, it should be around ISO 100 or ISO 200.

Using the ISO allows you to prioritize the aperture and shutter speed required. Sticking to your base ISO avoids you from aimlessly changing the settings back and forth.

When plenty of amounts of light are available, you should stick to the low ISO. This helps you to minimize the appearance of any noise.

If you are taking photos in low-light settings, you still have the option to change the shutter speed. While a low shutter speed is unable to shoot moving objects without motion blur, they can increase the exposure of a photo.

What is motion blur? Well, motion blur is essentially the camera failing to shoot a moving object. Making the objects that move in the photo leave a blurry trail or even look like a ghost.

In most cases having your ISO set to the lowest will just benefit you. Obviously, if you have set your ISO too low in situations where you direly need the ISO, your photo will just be too dark.

iso low
Photo by Thái Huỳnh

What happens if ISO is Too High?

If you use an ISO that is too high, you will risk overexposing your photo. Have you ever got flashed with a high lumen flashlight? It’s like doing that to the image.

There will always be times when you are forced to shoot at places with horrible lighting. It could be a meeting room, garage, and many more. In this situation, a higher ISO is completely acceptable.

So how do you properly pace your ISO?

First of all, using a longer shutter speed does help you brighten the photo. Sadly, the motion blur does not really go well with most themes.

A long shutter speed just will not cut when shooting fast-moving objects. You must choose something to sacrifice if you choose to bump the ISO up.

Would you rather shoot a blurry photo because you didn’t want to add the ISO? Or will you accept the fact that you need to raise the ISO because of the circumstances?

Remember the long shutter speed and its motion blur? Yes, it is in your best interest to avoid it while shooting fast-moving objects. Use the shorter shutter speed and compensate for the low exposure by increasing your ISO.

iso light
Photo by Rudolf Kirchner

How to Find Perfect ISO?

There is no perfect ISO ever. But there can be a key to it, which is your knowledge and experience.

Knowing the results and knowledge about the usage of ISO itself will not lead you to the perfect ISO. You need to pour those hours into practicing and consciously considering higher ISO on your shots.

Knowing the current gear that you bring and how you use it will also be helpful. Are you bringing your flash? Are you currently shooting while using a tripod or by handheld?

The more options there are, the less you need to rely on ISO.
If you plan to use a longer shutter speed, instantly set-up your tripod to avoid motion blur. If you can get proper lighting with a flash, then rest assured.

Most cameras have the auto ISO setting, which works superbly in low-light situations. You just input the maximum ISO and the camera will adjust the ISO without going over the maximum.

The camera will try to use longer shutter speeds when it reaches the max ISO. In the end, you cannot have everything.

In order to maximize your ISO usage, there are four main steps

  • Set the ISO to base value.
  • Choose the aperture that you need.
  • Set your shutter speed to the setting that provides the best exposure.
  • If there is motion blur on your subject, raise the ISO bit by bit use and faster shutter speeds until motion blur is gone.

If your ISO eventually gets too high and still needs more exposure. Then you need to use a larger aperture. Although this method sacrifices the focus and depth of field, it is better than a noisy image.

Forcing yourself to use the base ISO in dark conditions just limits your photos to the bad ones. Using an ISO that is too high will just ruin the image with its noise.

All should be balanced like a scale, there will be some sacrifices needed to keep it stable anyway.

Final Remarks

To recap this article

  • What is ISO? Well, it is not a part of exposure and it basically increases brightness.
  • ISO stands for “International Organization for Standardization”. Film standards merged into ISO, one thing led to another and here we are.
  • Common ISO values climb from 100, 200, 400, to 64000.
  • If your ISO is too low, you will not be able to shoot sharp pictures at dark conditions.
  • If your ISO is too high, your image will have visible noise. This makes images unappealing to the eye.
  • If you want the perfect exposure, always adjust your aperture first followed by shutter speed and ISO.

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